Safina missed three months last year because of a back injury.
"Slowly, I am starting to get some matches behind me," Safina said. "I'm still far from being at my best, but we are working day by day and with each win it helps me to get closer to where I want to be."
Mattek-Sands will face top-ranked Caroline Wozniacki on Thursday.
Mattek-Sands lost the one time she played Wozniacki, in the 2009 Italian Open.
"It's a good challenge for me and I like challenges," Mattek-Sands said. "You just got to go into the match knowing you're not going to get free points. For me, I'll stick to my same game plan. I'm going to play aggressive."
Information from The Associated Press was used in this report.